Congratulations on your new house. I will start by saying I have merv6 pre-filter and merv10 high effeciency filter just as you describe. Were I having allergy problems I would go up to 8 & 15. I had/have benifit of air flow and tempature differential testing which shows there is no concurns with restriction. What those who rally against good filters fail taking in to consideration is that if you pull a pleat filter out flat,there is a lot of surface area. 1) Is this the installing contactor advocating the removal of pre-filters?????? I would think the collective square inches of pre-filter would alow free flow unless the returns are under size to begain with. The only way to know is by calculating minium return size then compare to what is in place. 10 to 15% extra return size is prudent just as insurance in case of mistake ( such as omitting a turn in data) while calculating duct work. The installer should have done the calculations. If a secound contractor is challenging those,you need more and different help than can be found on the net. Don't waste money on cheapies. 2) I see no advantage in removing 1 or 2 while leaving another in place,unless the single remaining filter is in an exceptionaly dirty area. 3) There is no "rule of thumb"interval. You can establish your model through inspection of the filter(s). On a pleated filter,the bottom of vees will collect 95% of impurities starting out. As time passes,you can easyly see the grey collection creep from bottom of pleat toward top of pleat. The filter should be changed before the upper 1/3rd of pleat is covered in enough dust to hide the color of filter. The time required for that transisition on 5" will be much longer i you choose to use pre-filters. There is a very real possibility that the installing contractor put filters in the intakes to prevent construction materials getting into returns. It is possible he intended to abandon the 3 intake filters after home was complete. Discuss this with the installer to get best answers.

I have had a Cleaneffects since Oct 2007. I am very disappointed in its effectiveness. It was recommended highly by Consumers Reports at the time. They don�t recommend it that highly any more. We have severe respiratory problems here, so I was anxious to get it. I am embarrassed to admit that I was such a sucker, but hopefully it will help someone else. I was told by two different installers that the filter wouldn�t work with my old furnace, and modifying the furnace to make it work would cost more than a new furnace. I got the new furnace (Trane) even though my old one worked well, and it wound up costing me about $7000 to get both the furnace and the Cleaneffects filter. It would have been worth every penny if the filter had performed as Consumers Reports claimed, but it hasn�t even come close. I still had a couple of old room filters around and one night my wife got so stuffed up that she decided to pull one out and put it in the bedroom. It cleared her up right away. I bought a couple more room filters and we are using them extensively now. The air is much cleaner and the room filters cost a lot less than the whole-house system. I have maintained the system with diligence and in accordance with the manual, so those who say that system failures are due to laziness of the maintainer are wrong in this case. Here is why I think many users, such as me, are disappointed: When the contractors talk about how these things work, they say that enough air moves through the filter to account for changing all the air in the room several times a day. That is true, but it is misleading. If all the air in each room went through the filter even once a day, I believe the system would work pretty well. But in reality most of the air in any room takes the shortest path from the furnace output to the furnace intake. Some of the air gets exchanged (and therefore cleaned) over and over again, but most of the air remains undisturbed and un-cleaned. In my home, furnace outlets are near the ceiling as are the furnace intakes. So air near the floor doesn�t get churned up and seldom gets into the filter. A small room filter cleans the air near it, so the best solution is lots of small room air filters. In other words, a furnace-mounted whole house system is a flawed concept. In order for the system to work properly the furnace fan would have to run constantly at high speed and the house ducting would have to be designed so that the air will always be well-mixed. Air can�t be cleaned by the main filter if it never gets into it. You can make it work better with a lot of small fans, but if you are going to do that you might as well use small room filters. I wish Consumer is Reports had done a better job of reviewing this a few years ago, and I wish I had applied a little more common sense to my purchasing decision. It is true that I have a much better furnace now and possibly the best air cleaner I can get using a furnace-mounted system. That is looking at the bright side, but I often think about how I could have used that $7000 for other things. It was an expensive lesson.

The proper way to determine if you can install a pleated filter is with a Manometer gauge. Your contractor can take a reading between the supply air duct and return air duct and determine the Pressure Differential which registers in Inches of Water Column. He should include all internal devices which restrict the air flow, less the filter, and including the coil. Residential units have a typically low pressure differential, usually below 1" of pressure. Compare the reading with the manufacturers data for the filter (This is a clean filter rating) If you double the filter data this is what a dirty filter will require for pressure. Your contractor can best determine this. Remember that, except for certain areas of the country where smog is a problem, the air is more polluted in your home than outside. With cleaners, dust build-up, cooking grease, pet hair/dander,... Your contractor is correct about the fiberglass filters they are typically refered to as 30% efficient filters, which means 60% of the crud goes into the ductwork and builds up. Filters are now rated using the MERV rating system (Minimum Efficiency Rating Value) the higher the number, the better the filter. But they require more fan power. If you have a belt drive fan, your contractor may be able to resheave the fan (change pully/belt), but would have to verify the amp draw to make sure your not over amping the motor. Again your contractor would be best to determine this. You can get 1" pleated filters which would need to be changed more often than the 5" filters. Because of the greater depth of the 5" filter, it can hold more crud and you won't have to change as often. Personally, I like pleated filters, and think F.G. is a waste of money. How much does it cost in your area to get a duct cleaning? Compared to a $35 - $50 filter change? Hope that helps, Dan Martyn

Its really a messed up setup. It really cant be opened any larger. I mean it can but a whole new return box would have to be made and a gas line would have to be moved. It's doable but getting someone in here to do it and the extra cost would be quite a bit I assume. Which to have it done right that is the price you pay correct? There are parts that can trimmed out but as far as the 11 x 14 opening that as big as it can go. Like I said it was a horrible install. They hurried so bad that they tested the furnace to see if it worked. Then after they left he sent me a text wanting me to double check the gas line for leaks. I did the soapy water thing and they were leaking. One pipe was so loose I could easily turn it by hand. It's a wonder it didn't blow my house up when they turned on the furnace to test it. That's just the beginning of things that was installed wrong. So even at 11 x 14 it would be worth the trouble to install a 20 x20 filter grill? The 11 x 14 opening will not be a bottleneck even with a 20 x 20?